Jaw Winking

Also known as Marcus Gunn syndrome, jaw winking is a condition where one eyelid is droopy most of the time and jerks open when you open your mouth wide or move your jaw sharply to one side. In some cases the opposite is true - a droopy eyelid is yanked shut rather than opened. It's caused by an unusual arrangement of nerves connecting to the muscles of the face and jaw, and it is hereditary.